Headliners for vehicles are conventionally fiber glass or multi-layered laminated panels incorporating fiber glass and foam resin layers. The fiber glass or layers are placed between mirror image mold surfaces, compressed, heated to cure an incorporated resin adhesive, and then cut to shape at their periphery. Sometimes apertures for window openings, light fixtures, sun visors and the like are cut after molding. More often than not, in the assembly of the vehicle the headliner is inserted through the front window before the windshield is mounted. The typical headliner is concave downward and is sufficiently rigid to hold its shape when mounted along its side edges and with the central part of the headliner juxtaposed to the roof.
Various problems exist in the assembly of the headliner and one of those problems is that the headliner includes a decorative layer as the exposed surface visible to the passengers. Any folds, bends or blemishes in the visible surface creates a problem for one marketing the vehicle. As a practical matter, it is unacceptable to have exposed blemishes.
The headliner serves three other functions in addition to aesthetics which may be at odds with the concern for exposed blemishes. One problem is to provide a soft surface to minimize injury with head bumps. Fiber glass headliners are hard as are conventional headliners incorporating foamed resin. The only cushioning is in the decorative fabric. A second function is insulation from heat between the roof of the car and the interior or passenger compartment. The third function is sound insulation from exterior wind noise, engine noise, and the like.
A common solution to the problem of heat and noise insulation is the use of foamed resin layers in the headliner. The foamed resin is a better heat and sound barrier than resin impregnated fiber glass. Unfortunately, the foamed resin used is of the "closed cell" variety which includes a plurality of bubbles throughout the resin and a sealed skin surface on the surface of the resin layer. Foamed resin is initially quite rigid and with a sealed skin coating it will be even more rigid. Therefore, when the headliner must be bent or folded out of its original molded shape to get it into the proper position for installation in the vehicle it will often crack and/or rupture bubbles within the foamed layer itself. This often leaves a crease in the headliner which will be visible through the fabric. That is also true of fiber glass headliners. This exposed crease problem makes the flawed headliner unusable from a practical standpoint. As a consequence of the problem, the size of the windshield opening will often be dictated by the size of the headliner which must be inserted (whether the car manufacturer knows it or not).
The patent to Steward et al, U.S. Pat. No. 4,211,590, discloses a process for manufacturing a headliner for a passenger vehicle and the laminated contoured headliner includes one or more foamed resin thermoplastic layers of the closed cell variety sandwiched between a pair of rigid thermoplastic skin coats.
The patent to Harayama et al, U.S. Pat. No. 4,721,643, discloses another process for making a headliner and it too discloses a thermoplastic foamed resin layer of closed cells. The disclosure includes a laminate of a plurality of layers but all are structured so that there is a surface skin layer at each boundary of each foamed resin layer which inherently makes for rigidity and crease problems in assembling the headliner.
The patent to Landler et al, U.S. Pat. No. 4,478,660, discloses a different laminate and different process for making a foamed plastic layer in a decorative panel but it is even more rigid because of the incorporation of a hardenable resin mixed with wood dust filler in one layer.
The patent to Breitscheidel et al, U.S. Pat. No. 4,826,552, discloses a process for making a panel using an elastomeric, fiber glass reinforced, foam and a polymer substrate. It is clear from a reading of the patent that the rigidity of the resulting panel would make it inappropriate for a headliner.
The product on the market which is currently being used for headliners which is similar to the instant invention is a laminated panel which includes a decorative fabric layer for its exposed surface and the fabric is bonded directly to a closed cell foamed resin layer, the layer being coated on both sides with a hard resin skin. The next layer is a fiber glass mat which is sandwiched between the aforementioned foamed resin layer and another which is essentially identical. The backing layer is scrim. In both cases the closed cell foam used is coated on both sides and has an industry designation "120 ILD". The panel is relatively rigid and a fold will result in a permanent crease clearly visible through the fabric layer.